1. Field of the Invention
The invention generally relates to a display apparatus and a display method and, in particular, to a projection apparatus and a projection method.
2. Description of Related Art
In recent years, many kinds of displays, for example, liquid crystal displays (LCDs), plasma display panels (PDPs), organic light-emitting diode (OLED) displays, field emission displays (FEDs), and projection apparatus, are developed to replace conventional cathode ray tubes (CRTs). For most kinds of displays, the size of the displaying area of a display depends on the volume of the display. However, a projection apparatus with a relative small volume is capable of projecting an image frame with a large area. Therefore, the projection apparatus has its own advantage and is hard to be replaced.
When the projection apparatus projects an image frame onto a screen and when the optical axis of the lens of the projection apparatus is not perpendicular to the screen, the image frame on the screen has a keystone distortion and the height of the image frame is lengthened, which decreases the quality of the image frame. The keystone distortion of the image frame can be calibrated optically or electronically. However, an optical keystone calibration increases the cost of the projection apparatus, and the conventional electronic keystone calibration is complicated and thus also increases the cost of the projection apparatus.